2 .\" Copyright 1993, 1994, 1995 by Theodore Ts'o. All Rights Reserved.
3 .\" This file may be copied under the terms of the GNU Public License.
5 .TH MKE2FS 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
7 mke2fs \- create an ext2/ext3/ext4 filesystem
63 .I reserved-blocks-percentage
71 [^]\fIfeature\fR[,...]
96 .I last-mounted-directory
129 @JDEV@.B "mke2fs \-O journal_dev"
134 .\" No external-journal specific journal options yet (size is ignored)
137 .\" @JDEV@.I journal-options
141 @JDEV@.I volume-label
152 @JDEV@.I external-journal
158 is used to create an ext2, ext3, or ext4 filesystem, usually in a disk
159 partition (or file) named by
162 The file system size is specified by
166 does not have a suffix, it is interpreted as power-of-two kilobytes,
170 option is specified, in which case
172 is interpreted as the number of
174 blocks. If the fs-size is suffixed by 'k', 'm', 'g', 't'
175 (either upper-case or lower-case), then it is interpreted in
176 power-of-two kilobytes, megabytes, gigabytes, terabytes, etc.
181 will create the file system based on the device size.
197 will create a file system for use with ext3,
199 will create a file system for use with ext4, and so on.
201 The defaults of the parameters for the newly created filesystem, if not
202 overridden by the options listed below, are controlled by the
204 configuration file. See the
206 manual page for more details.
209 .BI \-b " block-size"
210 Specify the size of blocks in bytes. Valid block-size values are 1024,
211 2048 and 4096 bytes per block. If omitted,
212 block-size is heuristically determined by the filesystem size and
213 the expected usage of the filesystem (see the
217 is preceded by a negative sign ('-'), then
219 will use heuristics to determine the
220 appropriate block size, with the constraint that the block size will be
223 bytes. This is useful for certain hardware devices which require that
224 the blocksize be a multiple of 2k.
227 Check the device for bad blocks before creating the file system. If
228 this option is specified twice, then a slower read-write
229 test is used instead of a fast read-only test.
231 .B \-C " cluster-size"
232 Specify the size of cluster in bytes for filesystems using the bigalloc
233 feature. Valid cluster-size values are from 2048 to 256M bytes per
234 cluster. This can only be specified if the bigalloc feature is
237 man page for more details about bigalloc.) The default cluster size if
238 bigalloc is enabled is 16 times the block size.
240 .BI \-d " root-directory"
241 Copy the contents of the given directory into the root directory of the
245 Use direct I/O when writing to the disk. This avoids mke2fs dirtying a
246 lot of buffer cache memory, which may impact other applications running
247 on a busy server. This option will cause mke2fs to run much more
248 slowly, however, so there is a tradeoff to using direct I/O.
250 .BI \-e " error-behavior"
251 Change the behavior of the kernel code when errors are detected.
252 In all cases, a filesystem error will cause
254 to check the filesystem on the next boot.
256 can be one of the following:
260 Continue normal execution.
263 Remount filesystem read-only.
266 Cause a kernel panic.
269 .BI \-E " extended-options"
270 Set extended options for the filesystem. Extended options are comma
271 separated, and may take an argument using the equals ('=') sign. The
275 in earlier versions of
279 option is still accepted for backwards compatibility, but is deprecated.
280 The following extended options are supported:
283 .BI mmp_update_interval= interval
284 Adjust the initial MMP update interval to
286 seconds. Specifying an
288 of 0 means to use the default interval. The specified interval must
289 be less than 300 seconds. Requires that the
293 .BI stride= stride-size
294 Configure the filesystem for a RAID array with
296 filesystem blocks. This is the number of blocks read or written to disk
297 before moving to the next disk, which is sometimes referred to as the
299 This mostly affects placement of filesystem metadata like bitmaps at
301 time to avoid placing them on a single disk, which can hurt performance.
302 It may also be used by the block allocator.
304 .BI stripe_width= stripe-width
305 Configure the filesystem for a RAID array with
307 filesystem blocks per stripe. This is typically stride-size * N, where
308 N is the number of data-bearing disks in the RAID (e.g. for RAID 5 there is one
309 parity disk, so N will be the number of disks in the array minus 1).
310 This allows the block allocator to prevent read-modify-write of the
311 parity in a RAID stripe if possible when the data is written.
314 Create the filesystem at an offset from the beginning of the device or
315 file. This can be useful when creating disk images for virtual machines.
317 .BI resize= max-online-resize
318 Reserve enough space so that the block group descriptor table can grow
319 to support a filesystem that has
323 .B lazy_itable_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
324 If enabled and the uninit_bg feature is enabled, the inode table will
325 not be fully initialized by
327 This speeds up filesystem
328 initialization noticeably, but it requires the kernel to finish
329 initializing the filesystem in the background when the filesystem is
330 first mounted. If the option value is omitted, it defaults to 1 to
331 enable lazy inode table zeroing.
333 .B lazy_journal_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
334 If enabled, the journal inode will not be fully zeroed out by
336 This speeds up filesystem initialization noticeably, but carries some
337 small risk if the system crashes before the journal has been overwritten
338 entirely one time. If the option value is omitted, it defaults to 1 to
339 enable lazy journal inode zeroing.
344 will copy the extended attributes of the files in the directory
345 hierarchy specified via the (optional)
347 option. This will disable the copy and leaves the files in the newly
348 created file system without any extended attributes.
350 .BI num_backup_sb= <0|1|2>
353 file system feature is enabled this option controls whether there will
354 be 0, 1, or 2 backup superblocks created in the file system.
356 .B packed_meta_blocks\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
357 Place the allocation bitmaps and the inode table at the beginning of the
358 disk. This option requires that the flex_bg file system feature to be
359 enabled in order for it to have effect, and will also create the journal
360 at the beginning of the file system. This option is useful for flash
361 devices that use SLC flash at the beginning of the disk.
362 It also maximizes the range of contiguous data blocks, which
363 can be useful for certain specialized use cases, such as supported
366 .BI root_owner [=uid:gid]
367 Specify the numeric user and group ID of the root directory. If no UID:GID
368 is specified, use the user and group ID of the user running \fBmke2fs\fR.
369 In \fBmke2fs\fR 1.42 and earlier the UID and GID of the root directory were
370 set by default to the UID and GID of the user running the mke2fs command.
371 The \fBroot_owner=\fR option allows explicitly specifying these values,
372 and avoid side-effects for users that do not expect the contents of the
373 filesystem to change based on the user running \fBmke2fs\fR.
376 Set a flag in the filesystem superblock indicating that it may be
377 mounted using experimental kernel code, such as the ext4dev filesystem.
380 Attempt to discard blocks at mkfs time (discarding blocks initially is useful
381 on solid state devices and sparse / thin-provisioned storage). When the device
382 advertises that discard also zeroes data (any subsequent read after the discard
383 and before write returns zero), then mark all not-yet-zeroed inode tables as
384 zeroed. This significantly speeds up filesystem initialization. This is set
388 Do not attempt to discard blocks at mkfs time.
391 Specify the which quota types (usrquota, grpquota, prjquota) which
392 should be enabled in the created file system. The argument of this
393 extended option should be a colon separated list. This option has
396 feature is set. The default quota types to be initialized if this
397 option is not specified is both user and group quotas. If the project
398 feature is enabled that project quotas will be initialized as well.
404 to create a filesystem, even if the specified device is not a partition
405 on a block special device, or if other parameters do not make sense.
408 to create a filesystem even if the filesystem appears to be in use
409 or is mounted (a truly dangerous thing to do), this option must be
412 .BI \-g " blocks-per-group"
413 Specify the number of blocks in a block group. There is generally no
414 reason for the user to ever set this parameter, as the default is optimal
415 for the filesystem. (For administrators who are creating
416 filesystems on RAID arrays, it is preferable to use the
418 RAID parameter as part of the
420 option rather than manipulating the number of blocks per group.)
421 This option is generally used by developers who
422 are developing test cases.
424 If the bigalloc feature is enabled, the
426 option will specify the number of clusters in a block group.
428 .BI \-G " number-of-groups"
429 Specify the number of block groups that will be packed together to
430 create a larger virtual block group (or "flex_bg group") in an
431 ext4 filesystem. This improves meta-data locality and performance
432 on meta-data heavy workloads. The number of groups must be a power
433 of 2 and may only be specified if the
435 filesystem feature is enabled.
437 .BI \-i " bytes-per-inode"
438 Specify the bytes/inode ratio.
440 creates an inode for every
442 bytes of space on the disk. The larger the
444 ratio, the fewer inodes will be created. This value generally shouldn't
445 be smaller than the blocksize of the filesystem, since in that case more
446 inodes would be made than can ever be used. Be warned that it is not
447 possible to change this ratio on a filesystem after it is created, so be
448 careful deciding the correct value for this parameter. Note that resizing
449 a filesystem changes the number of inodes to maintain this ratio.
451 .BI \-I " inode-size"
452 Specify the size of each inode in bytes.
455 value must be a power of 2 larger or equal to 128. The larger the
457 the more space the inode table will consume, and this reduces the usable
458 space in the filesystem and can also negatively impact performance.
460 possible to change this value after the filesystem is created.
462 In kernels after 2.6.10 and some
463 earlier vendor kernels it is possible to utilize inodes larger than
465 extended attributes for improved performance.
467 stored in large inodes are not visible with older kernels, and such
468 filesystems will not be mountable with 2.4 kernels at all.
470 The default inode size is controlled by the
474 file shipped with e2fsprogs, the default inode size is 256 bytes for
475 most file systems, except for small file systems where the inode size
479 Create the filesystem with an ext3 journal. If the
481 option is not specified, the default journal parameters will be used to
482 create an appropriately sized journal (given the size of the filesystem)
483 stored within the filesystem. Note that you must be using a kernel
484 which has ext3 support in order to actually make use of the journal.
486 .BI \-J " journal-options"
487 Create the ext3 journal using options specified on the command-line.
488 Journal options are comma
489 separated, and may take an argument using the equals ('=') sign.
490 The following journal options are supported:
493 .BI size= journal-size
494 Create an internal journal (i.e., stored inside the filesystem) of size
497 The size of the journal must be at least 1024 filesystem blocks
498 (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
499 and may be no more than 10,240,000 filesystem blocks or half the total
500 file system size (whichever is smaller)
502 .BI location =journal-location
503 Specify the location of the journal. The argument
505 can either be specified as a block number, or if the number has a units
506 suffix (e.g., 'M', 'G', etc.) interpret it as the offset from the
507 beginning of the file system.
509 @JDEV@.BI device= external-journal
510 @JDEV@Attach the filesystem to the journal block device located on
511 @JDEV@.IR external-journal .
513 @JDEV@journal must already have been created using the command
515 @JDEV@.B mke2fs -O journal_dev
516 @JDEV@.I external-journal
519 @JDEV@.I external-journal
520 @JDEV@must have been created with the
521 @JDEV@same block size as the new filesystem.
522 @JDEV@In addition, while there is support for attaching
523 @JDEV@multiple filesystems to a single external journal,
524 @JDEV@the Linux kernel and
526 @JDEV@do not currently support shared external journals yet.
528 @JDEV@Instead of specifying a device name directly,
529 @JDEV@.I external-journal
530 @JDEV@can also be specified by either
531 @JDEV@.BI LABEL= label
534 @JDEV@to locate the external journal by either the volume label or UUID
535 @JDEV@stored in the ext2 superblock at the start of the journal. Use
536 @JDEV@.BR dumpe2fs (8)
537 @JDEV@to display a journal device's volume label and UUID. See also the
540 @JDEV@.BR tune2fs (8).
543 @JDEV@Only one of the
544 @JDEV@.BR size " or " device
545 @JDEV@options can be given for a filesystem.
548 Read the bad blocks list from
550 Note that the block numbers in the bad block list must be generated
551 using the same block size as used by
557 is a much simpler and less error-prone method of checking a disk for bad
558 blocks before formatting it, as
560 will automatically pass the correct parameters to the
564 .BI \-L " new-volume-label"
565 Set the volume label for the filesystem to
566 .IR new-volume-label .
567 The maximum length of the
568 volume label is 16 bytes.
570 .BI \-m " reserved-blocks-percentage"
571 Specify the percentage of the filesystem blocks reserved for
572 the super-user. This avoids fragmentation, and allows root-owned
575 to continue to function correctly after non-privileged processes are
576 prevented from writing to the filesystem. The default percentage
579 .BI \-M " last-mounted-directory"
580 Set the last mounted directory for the filesystem. This might be useful
581 for the sake of utilities that key off of the last mounted directory to
582 determine where the filesystem should be mounted.
587 to not actually create a filesystem, but display what it
588 would do if it were to create a filesystem. This can be used to
589 determine the location of the backup superblocks for a particular
590 filesystem, so long as the
592 parameters that were passed when the
593 filesystem was originally created are used again. (With the
595 option added, of course!)
597 .BI \-N " number-of-inodes"
598 Overrides the default calculation of the number of inodes that should be
599 reserved for the filesystem (which is based on the number of blocks and
602 ratio). This allows the user to specify the number
603 of desired inodes directly.
605 .BI \-o " creator-os"
606 Overrides the default value of the "creator operating system" field of the
607 filesystem. The creator field is set by default to the name of the OS the
609 executable was compiled for.
611 .B "\-O \fR[^]\fIfeature\fR[,...]"
612 Create a filesystem with the given features (filesystem options),
613 overriding the default filesystem options. The features that are
614 enabled by default are specified by the
616 relation, either in the
623 subsections for the usage types as specified by the
625 option, further modified by the
627 relation found in the
629 subsections for the filesystem and usage types. See the
631 manual page for more details.
632 The filesystem type-specific configuration setting found in the
634 section will override the global default found in
637 The filesystem feature set will be further edited
638 using either the feature set specified by this option,
639 or if this option is not given, by the
641 relation for the filesystem type being created, or in the
643 section of the configuration file.
645 The filesystem feature set is comprised of a list of features, separated
646 by commas, that are to be enabled. To disable a feature, simply
647 prefix the feature name with a caret ('^') character.
648 Features with dependencies will not be removed successfully.
649 The pseudo-filesystem feature "none" will clear all filesystem features.
651 For more information about the features which can be set, please see
656 Quiet execution. Useful if
661 Set the filesystem revision for the new filesystem. Note that 1.2
662 kernels only support revision 0 filesystems. The default is to
663 create revision 1 filesystems.
666 Write superblock and group descriptors only. This is an extreme
667 measure to be taken only in the very unlikely case that all of
668 the superblock and backup superblocks are corrupted, and a last-ditch
669 recovery method is desired by experienced users. It causes
671 to reinitialize the superblock and group descriptors, while not
672 touching the inode table and the block and inode bitmaps. The
674 program should be run immediately after this option is used, and there
675 is no guarantee that any data will be salvageable. Due to the wide
676 variety of possible options to
678 that affect the on-disk layout, it is critical to specify exactly
679 the same format options, such as blocksize, fs-type, feature flags, and
680 other tunables when using this option, or the filesystem will be further
681 corrupted. In some cases, such as filesystems that have been resized,
682 or have had features enabled after format time, it is impossible to
683 overwrite all of the superblocks correctly, and at least some filesystem
684 corruption will occur. It is best to run this on a full copy of the
685 filesystem so other options can be tried if this doesn't work.
688 .\" Check the device for bad blocks before creating the file system
689 .\" using the specified test.
692 Specify the filesystem type (i.e., ext2, ext3, ext4, etc.) that is
694 If this option is not specified,
696 will pick a default either via how
697 the command was run (for example, using a name of the form mkfs.ext2,
698 mkfs.ext3, etc.) or via a default as defined by the
700 file. This option controls which filesystem options are used by
701 default, based on the
703 configuration stanza in
704 .BR /etc/mke2fs.conf .
708 option is used to explicitly add or remove filesystem options that
709 should be set in the newly created filesystem, the
710 resulting filesystem may not be supported by the requested
712 (e.g., "\fBmke2fs \-t ext3 \-O extent /dev/sdXX\fR" will create a
713 filesystem that is not supported by the ext3 implementation as found in
714 the Linux kernel; and "\fBmke2fs \-t ext3 \-O ^has_journal /dev/hdXX\fR"
715 will create a filesystem that does not have a journal and hence will not
716 be supported by the ext3 filesystem code in the Linux kernel.)
718 .BI \-T " usage-type[,...]"
719 Specify how the filesystem is going to be used, so that
721 can choose optimal filesystem parameters for that use. The usage
722 types that are supported are defined in the configuration file
723 .BR /etc/mke2fs.conf .
724 The user may specify one or more usage types
725 using a comma separated list.
727 If this option is is not specified,
729 will pick a single default usage type based on the size of the filesystem to
730 be created. If the filesystem size is less than 3 megabytes,
732 will use the filesystem type
734 If the filesystem size is greater than or equal to 3 but less than
737 will use the filesystem type
739 If the filesystem size is greater than or equal to 4 terabytes but less than
742 will use the filesystem type
744 If the filesystem size is greater than or equal to 16 terabytes,
746 will use the filesystem type
750 will use the default filesystem type
754 Set the universally unique identifier (UUID) of the filesystem to
756 The format of the UUID is a series of hex digits separated by hyphens,
758 "c1b9d5a2-f162-11cf-9ece-0020afc76f16".
761 parameter may also be one of the following:
765 clear the filesystem UUID
768 generate a new randomly-generated UUID
771 generate a new time-based UUID
778 Print the version number of
783 Before overwriting a file system block, write the old contents of the block to
784 an undo file. This undo file can be used with e2undo(8) to restore the old
785 contents of the file system should something go wrong. If the empty string is
786 passed as the undo_file argument, the undo file will be written to a file named
787 mke2fs-\fIdevice\fR.e2undo in the directory specified via the
788 \fIE2FSPROGS_UNDO_DIR\fR environment variable or the \fIundo_dir\fR directive
789 in the configuration file.
791 WARNING: The undo file cannot be used to recover from a power or system crash.
795 If set to non-zero integer value, its value is used to determine how often
797 is called during inode table initialization.
800 Determines the location of the configuration file (see
801 .BR mke2fs.conf (5)).
803 .BI MKE2FS_FIRST_META_BG
804 If set to non-zero integer value, its value is used to determine first meta
805 block group. This is mostly for debugging purposes.
807 .BI MKE2FS_DEVICE_SECTSIZE
808 If set to non-zero integer value, its value is used to determine logical
812 .BI MKE2FS_DEVICE_PHYS_SECTSIZE
813 If set to non-zero integer value, its value is used to determine physical
817 .BI MKE2FS_SKIP_CHECK_MSG
818 If set, do not show the message of filesystem automatic check caused by
819 mount count or check interval.
823 has been written by Theodore Ts'o <tytso@mit.edu>.
826 is part of the e2fsprogs package and is available from
827 http://e2fsprogs.sourceforge.net.